Oleic acid (oleic acid) is an important natural chemical substance. It is one of the main fatty acids in lipid compounds in organisms. Pure oleic acid is free of Colored or nearly colorless liquid, usually commercially available oleic acid is a yellow transparent oily liquid with an oleic acid content of less than 80%, so we call oleic acid content of more than 90% high-purity oleic acid. High-purity oleic acid has good stability, high safety, and no irritation to the skin. In addition to being an important chemical reagent, it can also be processed into oleic acid derivatives, which is more suitable for use in medicine, cosmetics, information technology, bioengineering and other fields. . In the rubber and plastics industry, it is used to produce oleic acid amide (slip agent, release agent) and liquid composite heat stabilizer. Other industries are used to produce fine chemical products such as lubricants, emulsifiers, detergents, fatty alcohols and synthetic esters.

High-purity oleic acid can be prepared by physical, chemical and biological methods, including the following five types:

1. Emulsification Separation method:

Based on the different melting points of each fatty acid, it will appear in two phases: solid and liquid crystals at a certain temperature. This mixed fatty acid of different phases is dispersed in an aqueous solution containing surfactant and electrolyte to form a multi-phase dispersion system. Then, according to the different densities of each phase in the system, the heavy phase and the light phase are separated with the help of a centrifuge to obtain crude oleic acid. Then combine it with molecular distillation to produce high-purity oleic acid.

Process conditions:

Surfactants, such as alkyl benzene sulfonate, alkyl sulfonate, fatty alcohol sulfate, etc., have good wetting and dispersing capabilities. The effect is better when used in combination, and the surfactant concentration is controlled at 0.5%.

Electrolytes can include magnesium sulfate, aluminum sulfate, sodium sulfate, magnesium chloride, etc. Magnesium sulfate is generally used, with a concentration in the range of 1%-2%.

As for the crystallization temperature, it is generally better to choose a range of 10-15°C lower than the freezing point of fatty acids as the crystallization temperature.

Water to fully moisturize the fatty acids. The amount of water added to the plate is 2-4 times (mass ratio) of the mixed fatty acids.

2. Solvent separation method:

The difference in solubility of various fatty acids in organic solvents and their freezing points are used to separate mixed fatty acids. Such as methanol low-temperature crystallization separation method and acetone low-temperature crystallization separation method.

Compared with the emulsification separation method, although the solvent method requires the use of a large amount of flammable and sometimes expensive solvents, greater losses, and requires low freezing temperatures, it has good separation effects and high yields. The separation equipment is relatively simple.

3. Urea complex separation method:

The urea molecules are dissolved in the solvent and are oriented and arranged in a spiral lattice by hydrogen bonding to form A hexagonal prism-shaped cavity serves as the main body. Oleic acid and its sodium salt or saturated fatty acid serve as guests and are included in the cavity of the host, forming a host-guest system, that is, inclusions. Unsaturated fatty acids with two or more double bonds (such as linoleic acid, linolenic acid) and their salts have more double bonds in the molecules and complex molecular configurations, which increase their molecular volume and cannot Contained in the body cavity of urea. Under different conditions, the inclusions formed by urea and saturated fatty acids, and urea and the sodium salt of oleic acid were crystallized and separated. The sodium salt of unsaturated fatty acids containing two or more double bonds remains in the mother liquor. The inclusion of urea and oleic acid sodium salt is acidified and post-treated to obtain high-purity oleic acid.

4. Adsorption treatment and distillation separation method:

The adsorbents used in adsorption treatment include activated clay, activated carbon, silica gel, alumina, and aluminum silicate , ion exchange resin, zeolite, montmorillonite soil, synthetic adsorbent, etc., which can be used alone or mixed. The amount of adsorbent varies with the degree of refining of oleic acid and the quality of the product. It is generally 0.1%~5% of the quality of oleic acid. The adsorption treatment temperature is about 30~80°C, and the treatment time is about 20min-2h. Distillation operations generally use a process of subtractive distillation in the presence of inert gas. Keep residual pressure low and distillation temperature as low as possible.

5. Enzyme hydrolysis method:

Masao Suzuki and others used natural oils as raw materials to carry out enzymatic hydrolysis, and then used complexation method to further separate, Refining, and finally using molecular distillation method to obtain high-purity oleic acid. This method has the advantages of avoiding high temperature and using a large amount of organic solvents, and is easy to be industrialized.

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